Thermal processor employing a temperature compensation system

Abstract

A thermal processor for use in developing an image in an imaging material which is transported along a transport path through the thermal processor. The thermal processor includes a preheat assembly for preheating the thermally processable material to the threshold temperature. The preheat assembly includes a heated member having a major surface facing the thermally processable material. A dwell assembly is provided for thermal development of the image in the thermally processable material. Means are provided for moving the thermally processable material along the transport path through the preheat assembly and the dwell assembly including a roller assembly which contacts the thermally processable material. The roller assembly includes rollers positioned between the heated member and the thermally processable material. Means are provided for reducing optical density loss in the thermally processable material, including means for selectively changing the temperature of the heated member as the thermally processable material moves along the transport path.

1 . A thermal processor for use in developing an image in a thermally processable material which is transported along a transport path through the thermal processor, the thermal processor comprising:
 a preheat assembly for preheating the thermally processable material to a threshold temperature, including a heated member having a major surface facing the thermally processable material;   a dwell assembly for thermal development of the image in the thermally processable material;   means for moving the thermally processable material along the transport path through the preheat assembly and the dwell assembly, including a roller assembly which contacts the thermally processable material, and wherein the roller assembly includes rollers positioned between the heated member and the thermally processable material; and   means for reducing optical density loss in the thermally processable material, including means for selectively changing the temperature of the heated member as the thermally processable material moves along the transport path.   
     
     
         2 . The processor of  claim 1 , wherein the rollers are nested within the heated member. 
     
     
         3 . The processor of  claim 1 , wherein the rollers include a coating made of silicone. 
     
     
         4 . The processor of  claim 1 , wherein the means for selectively changing the temperature of the heated member includes means for selectively increasing the temperature of the heated member as the thermally processable material moves along the transport path, allowing the thermally processable material to reach the threshold temperature at the proper time. 
     
     
         5 . The processor of  claim 1 , wherein the means for selectively changing the temperature of the heated member includes:
 a position sensing system having an output signal representative of the position of the thermally processable material as it moves along the transport path;   a controller responsive to the position output signal for selectively changing the temperature of the heated member.   
     
     
         6 . The processor of  claim 5 , wherein the controller includes a table stored in memory, wherein the table includes values corresponding to a desired change in temperature of the heated member based on the position output signal. 
     
     
         7 . The processor  claim 1 , wherein the means for selectively changing the temperature of the heated member includes a computer program stored in memory. 
     
     
         8 . The processor of  claim 5 , wherein the thermally processable material includes a leading edge and a trailing edge, the position sensing system further includes a first sensor having a first output signal representative of the position of the leading edge of the thermally processable material along the transport path. 
     
     
         9 . The processor of  claim 5 , wherein the thermally processable material includes a leading edge and a trailing edge, the position sensing system further including an entrance sensor having a first output signal representative of the leading edge entering the thermal processor, and a second output signal representative of the trailing edge entering the thermal processor. 
     
     
         10 . The processor of  claim 9 , the position sensing system further including an exit sensor having a first output signal representative of the leading edge exiting the thermal processor and a second output signal representative of the trailing edge exiting the thermal processor. 
     
     
         11 . A method for developing an image in a thermally processable material transported along a transport path through a thermal processor, the thermal processor including a preheat assembly for preheating the thermally processable material to a threshold temperature, and a dwell assembly for thermal development of the image in the thermally processable material, the thermally processable material defined by a leading edge and a trailing edge, the method comprising the steps of:
 Operating a roller assembly to move the thermally processable material through the preheat assembly, including the step of contacting the thermally processable material with the roller assembly to move the thermally processable material along the transport path;   Heating the thermally processable material as it moves along the transport path through the preheat assembly using a heated member, wherein the roller assembly includes rollers positioned between the heated member and the thermally processable material; and   Changing the temperature of the heated member as the thermally processable material moves along the transport path reducing optical density loss in the thermally processable material.   
     
     
         12 . The method of  claim 11 , further comprising the step of nesting the rollers within the heated member, without contacting the heated member. 
     
     
         13 . The method of  claim 11  wherein the step of changing the temperature of the heated member includes the step of increasing the temperature of the heated member as the thermally processable material moves along the transport path, allowing the thermally processable material to reach the threshold temperature at the proper time. 
     
     
         14 . The method of  claim 11 , further comprising the step of sensing the position of the thermally processable material using a position sensing system as the thermally processable material moves along the transport path;
 providing a position output signal representative of the position of the thermally processable material along the transport path to a processor control system; and   changing the temperature of the heated member in response to the position output signal.   
     
     
         15 . The method of  claim 14 , wherein the step of changing the temperature of the heated member includes the step of storing a table in memory in the processor control system, wherein the table includes values correlating a desired change in temperature of the heated member based on the sensed position output signal. 
     
     
         16 . The method of  claim 14 , wherein the step of changing the temperature of the heated member in response to the position output signal includes the step of accessing a computer program stored in memory in the processor control system. 
     
     
         17 . The method of  claim 14 , wherein the step of sensing the position of the thermally processable material includes the steps of providing an entrance sensor having an output signal representative of the position of the leading edge as it enters the thermal processor. 
     
     
         18 . The method of  claim 14 , wherein the step of sensing the position of the thermally processable material includes the step of providing an entrance sensor having a first output signal representative of the position of the leading edge of the thermally processable material entering the thermal processor and a second output signal representative of the position of the trailing edge of the thermally processable material entering the thermal processor. 
     
     
         19 . The method of  claim 18 , wherein the step of sensing the position of the thermally processable material further includes the step of providing an exit sensor having a first output signal representative of the leading edge exiting the thermal processor and a second output signal representative of the trailing edge exiting the thermal process. 
     
     
         20 . A thermal processor for use in developing an image in a thermally processable material which is transported along a transport path through the thermal processor, the thermal processor comprising:
 A preheat assembly for preheating the thermally processable material to a threshold temperature, including a first heated member having a major surface facing the thermally processable material;   A transport system including a roller assembly positioned about the thermally processable material which contacts the thermally processable material for moving the thermally processable material along the transport path, the roller assembly including a plurality of rollers positioned between the first heated member and the thermally processable material; and   A thermal processor control system operably coupled to the first heated member and the transport system, the thermal processor control system including a controller for selectively changing the temperature of the heated member as the thermally processable material moves along the transport path.   
     
     
         21 . The thermal processor of  claim 20 , wherein the rollers are coated with foam. 
     
     
         22 . The thermal processor of  claim 20 , wherein the rollers are silicone coated. 
     
     
         23 . The thermal processor of  claim 20 , wherein the rollers which contact the thermally processable material are spaced from the heated member. 
     
     
         24 . The thermal processor of  claim 20 , further comprising a second heated member located adjacent the first heated member, wherein the first heated member and the second heated member are heated independent of each other. 
     
     
         25 . The thermal processor of  claim 20 , wherein the thermal processor is a flat bed processor. 
     
     
         26 . The thermal processor of  claim 20 , further comprising an entrance sensor, wherein the entrance sensor provides an output signal to the controller representative of the position of the thermally processable material along the transport path. 
     
     
         27 . The thermal processor of  claim 26 , wherein the output signal includes a first output signal representative of the leading edge of the thermally processable material entering the thermal processor and a second output signal representative of the trailing edge of the thermally processable material entering the thermal processor. 
     
     
         28 . The thermal processor of  claim 27 , further wherein the controller is responsive to the first output signal for increasing the temperature of the heated member. 
     
     
         29 . The thermal processor of  claim 27 , wherein the controller is responsive to the second output signal for decreasing the temperature of the heated member. 
     
     
         30 . The thermal processor of  claim 20 , further comprising an exit sensor, wherein the exit sensor provides an output signal to the controller representative of the position of the thermally processable material along the transport path. 
     
     
         31 . The thermal processor of  claim 30 , wherein the output signal includes a first output signal representative of the leading edge of the thermally processable material exiting the thermal processor. 
     
     
         32 . The thermal processor of  claim 31 , wherein the controller is responsive to the first output signal for increasing the temperature of the heated member. 
     
     
         33 . The thermal processor of  claim 31 , wherein the output signal includes a second output signal representative of the trailing edge of the thermally processable material exiting the thermal processor. 
     
     
         34 . The thermal processor of  claim 33 , wherein the controller is responsive to the second output signal for decreasing the temperature of the heated member.